Lead Land Steward Volunteer Henry DiRocco plucks a Sahara mustard plant out from between two black sage plants. Simple hand weeding is critical to stopping the spread of this invasive plant.

Wildflowers are starting to appear in local canyons, but not all of these flowers are happy harbingers of spring. Some blooms are signs of invasive weeds threatening native plants and wildlife of the Irvine Ranch Natural Landmarks. And while spring is the season to spot native wildflowers, it’s also a critical time to remove one of the most dangerous and invasive threats to our protected wild lands: Sahara mustard. You can help by volunteering to remove this invasive weed and help restore wildlife habitat.

Sahara mustard (Brassica tournefortii) is a highly aggressive invasive weed that is more of an immediate threat to native flora and fauna than other, more-prevalent mustard such as black mustard (Brassica nigra). Despite Sahara mustard’s tiny, pale yellow flowers that look pretty for a short while, its ability to quickly and easily invade and replace healthy habitat makes it a prominent threat to the Landmarks. The weed can quickly spread its seed, grow rapidly, making it a top priority for removal before it establishes too much of a hold within the Landmarks. When invasive weeds drive out native plants, they also drive out the wildlife that depends on native plants for food and shelter. Public support is vital to stopping the weed’s spread and ensuring the continued protection of one of Orange County’s most diverse open spaces.

Irvine Ranch Conservancy staff and Land Steward volunteers have been working hard to keep Sahara mustard at bay, and have arranged several community volunteer opportunities to encourage members of the public to participate in stopping this dangerous weed. Despite its aggressive nature, removing Sahara mustard plants is relatively easy, mostly done by hand. Not only will volunteers be making an immediate impact on supporting wildlife habitat, but enjoying beautiful green hillsides and spectacular views as they work.

There are several volunteer opportunities for those interested in removing this invasive weed and restoring native habitat in the Landmarks. By removing new mustard plants at Sahara Mustard Pull at Loma Ridge on Thursday, March 3, you’ll be directly contributing to the protection of native habitat in OC Parks’ Limestone Canyon Nature Preserve. On Saturday, March 5, the City of Irvine will offer a similar program led by Conservancy volunteers removing the invasive weed during Sahara Mustard Pull at Orchard Hills. The event is a great opportunity to enjoy an easy trail while helping to care for the land. Additional volunteer opportunities to remove Sahara mustard will occur on Friday, March 11, in Orchard Hills, and Thursday, March 24, on Loma Ridge in Limestone Canyon.

There are a few reasons why Sahara mustard is such an immediate threat. The plant starts growing earlier than most native plants, and the leaves at its base spread out in a wide rosette pattern. This weed also out-competes native plants because its seeds are extremely hardy, germinate quickly, and can thrive in both wet and dry conditions. Each adult plant can produce as many as 10,000 seeds that remain in the soil for several years and spread rapidly – meaning land managers are always working against the clock each year to remove the plants before they go to seed. While shorter in size than black mustard, the more aggressive Sahara mustard’s spindly stems grow just as quickly and dies annually, becoming fuel for fire.

​Volunteers assisting in the removal of Sahara mustard will work with science staff and trained stewardship leaders during these events, which will include bending, kneeling and walking across slopes and uneven terrain. All training and tools are provided, and kids ages 12 and over are welcome to participate with their parent or guardian. To find additional volunteer opportunities, click here. All programs are free with required registration, which closes at 4 p.m. the day prior to the event. For more details on these activities or to register, click the titles above or visit LetsGoOutside.org/activities.

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Welcome to the Irvine Ranch Conservancy "News from the Field" blog. These articles are written by Conservancy staff about activities and projects in and near the Irvine Ranch Natural Landmarks.